This is 99% invisible.

I'm Roman Mars.

Producer Liza Yeager recently did something that will become pretty common with the next generation of kids.

She asked her grandma to show her her tattoo.

Can you just describe what the tattoo looks like?

That's Liza.

Oh, the tattoo.

And that's my grandma, Carol Fischler, showing me her tattoo.

It's very tiny.

I think it's maybe 5-8ths of an inch and it looks like a little hand mirror.

Although it's definitely not a hand mirror.

It's a little circle and then a line going off to the side of it.

And then there's a cross over that line because my blood type is O+.

It's a tiny tattoo of her blood type right on her ribcage and just under her left arm.

Okay, so do you think that you can just walk me through step by step the whole process of getting the tattoo?

Oh, well, it was pretty straight forward.

All of the kids whose parents had signed the little slip word taking marched out of our classroom and down the hall.

And yeah, this was in school.

This happened in Lake County, Indiana.

It was 1952 and my grandma was 16.

And at the first station that you came to, they pricked your finger and squeezed a little drop of blood onto a little card

and determined what your blood type was.

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